The present invention relates to a fuel tank unit of a motorcycle having an improved mounting structure.
There has been provided a motorcycle having a device for transmitting, when fuel received in a fuel tank is decreased to an amount of less than a prescribed amount, information to a rider accordingly.
With respect to such a device, as disclosed in Japanese Utility Model Publication No. S58-37746, an opening is formed on the bottom of the fuel tank and a float type fuel level gauge is inserted in the fuel tank through such opening. The fuel level gauge is integrally provided with a cover, which closes the opening.
With respect to the devices, for example, as disclosed in Japanese Patent Laid-Open Publication No. H1-257686, the fuel tank includes therein a fuel pump and the fuel pump is provided with a fuel sensor utilizing a thermistor, which operates by the utilization of a change in temperature of the thermistor depending on change in its resistance. The thermistor is mounted at a prescribed level in the fuel tank so as to detect, as resistance value, difference in temperature between one state where the thermistor is submerged in a liquid and another state where it exists in air. When fuel is decreased to an amount of a level less than the prescribed level, the thermistor gives information to a rider that the fuel is decreased to the amount less than the prescribed amount.
However, in the structure in which the fuel tank is provided with the float type fuel level gauge, provision of the fuel pump in the fuel tank requires formation of a specific opening for the fuel pump. A layout of the fuel tank makes it hard to secure a wide flat surface on which the opening is to be formed, on the bottom of the fuel tank. Especially, although a sufficient distance is required between the movable float and the fuel pump to prevent interference therebetween, it is difficult to secure a wide space thereto for the reasons mentioned above.
The fuel sensor utilizing the thermistor has advantage in the location of space. However, such a fuel sensor merely indicates as whether fuel in the fuel tank exceeds the prescribed level or not, and more specifically, such a fuel sensor does not provide a continuous visual information on the decreasing in an amount of fuel, unlike the float type fuel gauge. As a result, information that the fuel is decreased to an amount less than the prescribed amount is suddenly given, thus causing unfavorable results.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a fuel tank unit of a motorcycle, which permits to mount the float type fuel level gauge and the fuel pump through a single (one common) opening.
This and other objects can be achieved according to the present invention by providing a fuel tank unit of a motorcycle in which an air cleaner and a fuel tank unit are disposed above an engine, said fuel tank unit comprising:
a fuel tank body having a front half portion and arear half portion, the front half portion being provided with a recess portion in which the air cleaner is received, the recess portion being provided on a front side of a bottom of the fuel tank body so as to have an opening opened downward, the rear half portion of the fuel tank body serving as a substantial capacity section;
a fuel pump disposed inside the substantial capacity section; and
a fuel level gauge device mounted on a top portion of the fuel pump to detect a fuel level in the fuel tank body, the fuel level gauge including a gauge body disposed above the fuel pump and an arm member pivoted on the gauge body and having a free end swingable above the fuel pump.
In a preferred embodiment, the arm member having, at a free end thereof, a float is pivoted so as to be swingable up and down on a plane which is in parallel with a vertical plane connecting a ground surface and a longitudinal axial line (i.e., a plane including a longitudinal axial line) of the motorcycle in an advancing direction thereof.
The fuel pump is mounted in the fuel tank body so that a longitudinal axis of the fuel pump is inclined with a rear end thereof lifted higher than a front end thereof.
The arm member has a center of a swing motion positioned substantially at a middle portion in a depth direction of the substantial capacity section of the fuel tank body. The arm member has an axial line, which is set to be inclined upward from the center of the swing motion of the arm member at an upper limit position of a measuring range of the fuel gauge body, and the fuel tank body is provided with an upper rear portion having an inclined surface, which is inclined upward so as to be substantially in parallel with the axial line of the arm member at the limit position thereof.
According to the characters and structures of the present invention mentioned above, since the float type fuel level gauge device is provided on a top portion of the fuel pump, and the arm member is pivoted on the gauge body of the fuel level gauge device so that a free end of the arm member is swingable above the fuel pump, it is unnecessary to additionally form any specific opening into which the gauge is to be inserted and eliminate the restriction of mounting place of the fuel pump.
In addition, by connecting swingably the arm member having it free end the float to the gauge body so as to swing up and down on the plane, which is in parallel with the vertical plane connecting the longitudinal line of the motorcycle in the advancing (cruising) direction with the ground surface, the bending moment, which is applied to the swing axis of the arm member, can be reduced, thus improving durability.
In addition, by fixing the fuel pump to the fuel tank so that the longitudinal axis of the fuel pump is inclined with its rear end lifted higher than its front end, it is made possible to increase the measurement range of fuel level.
Further, by positioning the center of the swing motion of the arm member substantially at the middle portion in the depth direction of the substantial (essential) capacity member of the fuel tank, it is also made possible to decrease the length of the arm member.
Furthermore, the position of the arm member, which is swung to the upper limit position of the measuring range of the gauge body, is determined so that the axial line of the arm member is inclined upward from the center of the swing motion thereof. Accordingly, when the arm member is kept in that upper limit position, the inclined surface on the upper plate of the rear portion of the fuel tank is also inclined upward so as to be substantially in parallel with the axial line of the arm member. It is therefore possible to provide an improved riding feeling.
It is to be noted that the nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.